Advanced MathEasy–MediumReflection of an exponential graph across the y-axis
Advanced Math practice question
In the xy-plane, which of the following is an equation of the reflection of the graph of y = 2ˣ across the y-axis?
- A. y = 2⁻ˣCorrect
- B. y = −2ˣ
- C. y = 2ˣ − 1
- D. y = (1/2)ˣ + 1
Answer: A. y = 2⁻ˣ
Reflecting across the y-axis replaces x with −x: y = 2⁻ˣ (which equals (1/2)ˣ).
Why the other answers are wrong
- B. y = −2ˣ
- −2ˣ is the reflection across the x-axis.
- C. y = 2ˣ − 1
- Subtracting 1 shifts the graph down.
- D. y = (1/2)ˣ + 1
- (1/2)ˣ is the reflection, but the +1 shifts it up.
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